Braid reinforced flexible hose

ABSTRACT

A braided hose reinforcement comprises left and right turning strips. Each of said strips comprises a number of elongated metal elements embedded in a matrix of a polymer material.

FIELD OF THE INVENTION

[0001] The invention relates to a braided hose reinforcement.

BACKGROUND OF THE INVENTION

[0002] Hoses, for example hydraulic and pneumatic hoses, conventionallycomprise a flexible inner tube, such as a rubber or plastic inner tubesurrounded by one or more tubular braids of metal wires.

[0003] Since these hoses are used for conveying high pressure fluids orgases, they have to withstand the forces of the pressure within thehose. In order to obtain a high impulse strength, high strength carbonsteel wires are utilized as reinforcing elements.

[0004] In a still continuing effort to save weight of a hosereinforcement and to increase the flexibility, there is a trend to usewires with a higher tensile strength.

[0005] However, because of the high internal pressure, high transversalstresses are applied on the reinforcing elements. This has asconsequence that the hose can not be utilized at its full strength.

[0006] To minimize the stresses on the wires, the strips can be braidedin such a way that the braided structure does not provide 100% coverageof the inner tube but for example only 80 or 85% coverage. Theseparation between adjacent strips permits some freedom of movement ofthe wires during flexing and/or application of fluid pressure to thehose and results in good stress transfer from wire to wire.

[0007] Other ways to minimize the stresses applied on the wires is toprovide a hose reinforcement which comprises several superimposed layersof wires. Such reinforcement structures, however, have the disadvantageof a higher weight.

SUMMARY OF THE INVENTION

[0008] It is an object of the present invention to provide a braidedhose reinforcement with an increased strength and endurance.

[0009] It is also an object of the invention to decrease the weight andto increase the flexibility of a hose reinforcement while maintaining ahigh strength.

[0010] According to a first aspect of the invention, a braided hosereinforcement is provided. The hose reinforcement comprises a number ofleft and right turning strips. The left turning strips are bent in sucha way that they subsequently run above and under the right turningstrips; while the right turning strips are bent so that theysubsequently run above and under the left turning strips.

[0011] Each of the strips comprises a number of elongated metal elementsembedded in a matrix of a polymer material.

[0012] The metal elements are preferably located parallel in the planeof the strip.

[0013] The metal elements are preferably high carbon steel wires, butcan also be stainless steel wires, steel bundles or steel cords.

[0014] Conventionally, a hose reinforcement comprises braided strands ofmetal wires.

[0015] Since each strand passes alternately over and under atransversely directed strand, the wires of the strands are deformed.

[0016] Consequently, stresses are created on the wires, moreparticularly on the segments of the wires between adjacent overlying andunderlying transverse strips.

[0017] The stresses created in each segment will depend on the level ofpinching exerted by the wires lying over and under the wire.

[0018] This pinching gives rise to a rather complex form of stress,which is not simply tensile or traction, but is also includingtransversal forces on certain points along the wires. The wires locatedat the outer side of a strand suffer most from this pinching effect.

[0019] It has been shown that transversal forces have a negative impacton the breaking load of a metal wire.

[0020] Consequently, due to the pinching effect, creating transversalcontact stresses, the high tensile wire can not be used at its fullpotential.

[0021] This means that the full strength of the hose remains limitedalthough high tensile wire is used.

[0022] Therefore, according to the present invention, the metal wiresare embedded in a polymer matrix.

[0023] By embedding the metal wires in a polymer matrix the pinchingeffect is reduced. Consequently, the loss in breaking load is reduced oreven avoided.

[0024] A strip comprises preferably between two and ten steel wires,more preferably a strip comprises between four and eight wires.

[0025] The strips have a width preferably between 3 and 25 mm and athickness preferably between 0.2 and 5 mm.

[0026] The steel wires preferably have a diameter between 0.10 and 0.90mm, for example 0.20 mm.

[0027] The wires may be round wires or they may be flattened, forexample to wires having a rectangular cross-section or a rectangularcross-section with rounded edges.

[0028] The steel wires embedded in the strips preferably have a carboncontent between 0.70% and 1.20% and a tensile strength between 2150 and4000 N/mm².

[0029] A possible method of manufacturing a strip is by coextrusion.

[0030] As polymer material any elastomeric material, such as rubber orany thermoplastic material can be used.

[0031] With a thermoplastic material is meant any thermoplast and anythermoplastic elastomer.

[0032] Examples of suitable thermoplastic materials are: polyethylene(PE), polypropylene (PP), polystyrene (PS), polyethylene terephthalate(PET), polyethylene napthalate (PEN), polybuteen terephthalate (PBT)polyvinylchloride (PVC), polyester, polyamide (PA), polyimide (PI),polycarbonate (PC), styrene acrilonitryl (SAN),acrylonitril-butadiene-styrene (ABS), thermoplastic polyurethane (TPU),thermoplastic polyolefins (TPO), thermoplastic copolyetheresters,copolymers of these polymers or similar materials.

[0033] In order to assure a good adhesion between the metal and thepolymer material, an adhesion promoter can be applied on the metalelements. Possible adhesion promoters are bifunctional coupling agentssuch as silane compounds. One functional group of these coupling agentsis responsible for the binding with the metal or metal oxides; the otherfunctional group reacts with the polymer.

[0034] More details about these coupling agents can be found in the PCTapplication WO 99/20682.

[0035] Other suitable adhesion promoters are aluminates, zirconates ortitanates.

[0036] The steel wires may also be coated with a metal or metal alloycoating to assure satisfactory adhesion to the polymer material.

[0037] Suitable coatings are for example copper or zinc or alloys ofthese metals, such as brass.

[0038] The braided hose reinforcement may comprise steel wires arrangedin one layer or may comprise multiple layers.

[0039] In case the hose reinforcement comprises more layers, a thinpolymer layer may be present between two different layers to providestress transfer from one layer to the other.

[0040] According to a second aspect of the invention a hose, pipe ortube comprising a hose reinforcement as described above is provided.

[0041] According to a further aspect a method of manufacturing a hosereinforcement according to the present invention is provided.

[0042] This method comprises the steps of

[0043] providing a number of strips, each of said strips comprising anumber of elongated metal elements embedded in a matrix of a polymermaterial;

[0044] braiding said strips to form the reinforcement.

BRIEF DESCRIPTION OF THE DRAWINGS

[0045] The invention will now be described into more detail withreference to the accompanying drawings wherein

[0046]FIG. 1 shows a reinforced hose according to the present invention;

[0047]FIG. 2 is an illustration of a strip comprising elongated metalelements embedded in a matrix of a polymer material.

DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

[0048]FIG. 1 shows a flexible hose 10.

[0049] The hose comprises:

[0050] an inner tube 12;

[0051] a reinforcement structure 14, comprising at least one tubularbraid;

[0052] an outer cover 16.

[0053] The inner tube and the outer cover may be made of any suitablerubber or thermoplastic elastomer known to be useful in hoseapplications. The reinforcement 14 comprises strips 18 passingalternately over and under transversely directed strips 18′.

[0054]FIG. 2 shows a strip 18.

[0055] The width of the strip is 15 mm, the thickness is 3 mm.

[0056] A strip 18 comprises nine steel wires 20 having a diameterbetween 0.10 and 0.90 mm.

[0057] The steel wires are for example steel wires with a carbon contentbetween 0.70% an 1.20% or high carbon micro-alloyed steel wirescomprising from 0.70% to 1.20% C, 0.10 to 1.2% Mn and up to 0.40% ofchromium, cobalt, molybdenum, nickel, and/or vanadium.

[0058] The tensile strength of the wires is preferably higher than 2800N/mm².

[0059] The strip comprises polyurethane (PU) as matrix material 22. ThisPU material is applied by extrusion.

[0060] Possibly, the steel wires located at the outer sides of a stripmay be replaced by steel wires having a lower tensile strength than thesteel wires located in the central part of the strip.

[0061] In a preferred embodiment the steel wires located at the outersides of a strip have a tensile strength which is at least 10% lowerthan the tensile strength of the steel wires located in the central partof the strip. More preferably, the tensile strength of the steel wireslocated at the outer sides of a strip is more than 20% lower than thetensile strength of the steel wires located in the central part of thestrip.

[0062] For example, the steel wires located at the outer sides of astrip may be stress-relieved steel wires. These steel wires preferablyhave an elongation at rupture exceeding 4%.

[0063] Alternatively, the steel wires located at the outer side of astrip are wires having a lower carbon content than the steel wireslocated in the central part of the strip.

[0064] The carbon content of the steel wires located at the outer sidesof a strip is for example lower than 0.80%.

1. A braided hose reinforcement comprising left and right turningstrips, said left turning strips being bent so that they subsequentlyrun above and under said right turning strips and vice versa, each ofsaid strips comprising a number of elongated metal elements embedded ina matrix of a polymer material.
 2. A braided hose reinforcementaccording to claim 1, wherein said strip has a width ranging from 3 to25 mm and a thickness ranging from 0.2 to 5 mm.
 3. A hose reinforcementaccording to claim 1, wherein said elongated metal elements are steelwires, steel bundles or steel cords.
 4. A hose reinforcement accordingto claim 3, wherein said steel wires are round or flat steel wires.
 5. Ahose reinforcement according to claim 3, wherein said elongated metalelements are steel wires with a tensile strength higher than 2150 N/mm².6. A hose reinforcement according to claim 1, wherein the number of saidelongated metal elements ranges from 2 to
 10. 7. A hose reinforcementaccording to any one of the preceding claims, wherein said polymermaterial is an elastomeric or thermoplastic material.
 8. A hose, pipe ortube comprising a hose reinforcement according to any one of claims 1 to7.
 9. A method of manufacturing a hose reinforcement according to anyone of claims 1 to 7, said method comprises the steps of providing anumber of strips, each of said strips comprising a number of elongatedmetal elements embedded in a matrix of a polymer material; braiding saidstrips to form the reinforcement.